Manufacturers, such as automobile manufacturers, have recently refocused efforts to reduce or attenuate the noise and vibration of their products. Because of these efforts, many treatments have been devised for the various panels. Traditional means for quieting panels would include mastics, spray-on deadeners, etc. Each of these systems has its shortcomings.
Mastics are asphaltic patches, which are attached to metal surfaces and hardened during a heat-elevated painting process. Heat activated mastics are also used for damping resonances. Disadvantages of mastics include: build variations due to manual placement; airborne paint contamination resulting in paint quality issues; labor required for installation; inconsistent melt characteristics; non recyclability; susceptibility to damage during installation; packaging limitations due to thickness of mastics; providing only localized damping; and assembly line space requirements.
Spray-on deadeners are sprayed treatments that are typically applied via a robot or manually to panel. Spray-on deadeners provide a noise control barrier. Disadvantages of spray-on deadeners include: masking requirement for spray applications; non-recyclability; process limited by overspray and dripping; robot requirement for application; assembly line space requirement; on-going maintenance of robots; and only localized damping coverage.
Because of the limitations of the above-mentioned treatments, designers and engineers have begun to use panel constrained layer damper treatments for noise and vibration attenuation, especially to diminish the propagation of structural noise and the transmission of airborne noise. The panel constrained layer damper treatment provides both high damping effectiveness and structurally rigidity, therefore is a preferred method of damping both airborne and structural borne vibrations. The panel constrained layer damper includes a panel having a visco-elastic layer attached thereto. The prior art panel constrained layer dampers are formed by stamping the panel and die-cutting the visco-elastic layer to match the dimensions of the panel. The visco-elastic layer is then attached to the panel by various methods such as, for example, tabs or heat staking to form a panel constraining layer damper, or PCL damper. The formation of the PCL damper has traditionally been labor intensive and the visco-elastic layer may inadvertently become separated from the panel if not properly secured. The PCL damper is subsequently attached to a substrate, such as an automotive body panel, to form the panel constrained layer damper treatment.